Compression Ratio Question.......
Race Director
Joined: Sep 2000
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From: The Top of Utah
Originally Posted by jsup
Ok, last annoying question as to my build.......
The stock CR was 10.25:1. The only thing I changed was the gasket. I went from .050 to .040. What is my CR now.
The stock CR was 10.25:1. The only thing I changed was the gasket. I went from .050 to .040. What is my CR now.
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Team Owner
Joined: Oct 2004
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From: Bergen County, NJ Democrats, doing for the country what they did for Michigan
Just do the math. You know the bore, stroke, and the compression ratio. With that info, you can figure backward to the clearance volume. The clearance volume includes all the volumes you don't have specific numbers on, needed for a calculator, deck volume, piston dome or notch volume, gasket volume, etc., all in one package. Add the additional gasket volume to the old clearance volume and re-figure the new compression ratio. Easy.
RACE ON!!!
RACE ON!!!
Melting Slicks
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From: Kathleen FL
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From: OBAMA IS HITLER
you really won't know what your c/r is. factory tolerance stack can be all over the place. for instance, yes while it's true that the "established stock" deck height is 0.025", mine measured out to 0.005", and it was never touched. that's quite a difference.
i'd say it's safe to still run 91 octane gas for about half the year. during the summer months especially, i'd run 93 octane and you should be good to go.
those two tts datamaster datalogs are going to be important. this is why you need to get them done & analyzed as soon as possible. you'll see knock counts that you may not hear -- this is very important. then alvin can pull back on timing just a tad in certain areas to compensate.
i'd say it's safe to still run 91 octane gas for about half the year. during the summer months especially, i'd run 93 octane and you should be good to go.
those two tts datamaster datalogs are going to be important. this is why you need to get them done & analyzed as soon as possible. you'll see knock counts that you may not hear -- this is very important. then alvin can pull back on timing just a tad in certain areas to compensate.
Last edited by Red Tornado; Feb 20, 2008 at 10:38 PM.
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From: One day you're a Comet...the next day you're dust... Arkansas
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Le Mans Master
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From: Valparaiso
Let me explain myself better :
1989 :
Compression Ratio 9.5:1
Horsepower 245 hp @ 4,300 rpm (coupe w/ 3.07:1 axle)
240 hp (convert.)
Torque 340 lb-ft @ 3,200 rpm
1990 :
Compression Ratio 10.25:1
Horsepower 250 hp @ 4,400 rpm (coupe)
245 hp @ 4,000 rpm (convert.)
Torque 350 lb-ft @ 3,200 rpm (coupe)
345 lb-ft @ 3,200 rpm (convert.)
Ok 1990 got 5 HP more ....
its because of the added compression ??????
5 HP with flat tops ? its too little
from 9.5 :1 to 10.25:1 its 5 hp ?
1989 :
Compression Ratio 9.5:1
Horsepower 245 hp @ 4,300 rpm (coupe w/ 3.07:1 axle)
240 hp (convert.)
Torque 340 lb-ft @ 3,200 rpm
1990 :
Compression Ratio 10.25:1
Horsepower 250 hp @ 4,400 rpm (coupe)
245 hp @ 4,000 rpm (convert.)
Torque 350 lb-ft @ 3,200 rpm (coupe)
345 lb-ft @ 3,200 rpm (convert.)
Ok 1990 got 5 HP more ....
its because of the added compression ??????
5 HP with flat tops ? its too little
from 9.5 :1 to 10.25:1 its 5 hp ?
Last edited by Calderone; Feb 21, 2008 at 08:08 PM.
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Team Owner
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From: Bergen County, NJ Democrats, doing for the country what they did for Michigan
Team Owner
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From: OBAMA IS HITLER
they pussified the 90-91 camshaft specs in order to offset/cut power, as the LT1 was being rolled out and GM could never have claimed a 50chp difference, would have been more like 25-35chp; this doesn't advertise as well and have a nice ring to it that 50hp does.
Last edited by Red Tornado; Feb 22, 2008 at 12:08 AM.
Team Owner
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From: Athens AL
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Let me explain myself better :
1989 :
Compression Ratio 9.5:1
Horsepower 245 hp @ 4,300 rpm (coupe w/ 3.07:1 axle)
240 hp (convert.)
Torque 340 lb-ft @ 3,200 rpm
1990 :
Compression Ratio 10.25:1
Horsepower 250 hp @ 4,400 rpm (coupe)
245 hp @ 4,000 rpm (convert.)
Torque 350 lb-ft @ 3,200 rpm (coupe)
345 lb-ft @ 3,200 rpm (convert.)
Ok 1990 got 5 HP more ....
its because of the added compression ??????
5 HP with flat tops ? its too little
from 9.5 :1 to 10.25:1 its 5 hp ?
1989 :
Compression Ratio 9.5:1
Horsepower 245 hp @ 4,300 rpm (coupe w/ 3.07:1 axle)
240 hp (convert.)
Torque 340 lb-ft @ 3,200 rpm
1990 :
Compression Ratio 10.25:1
Horsepower 250 hp @ 4,400 rpm (coupe)
245 hp @ 4,000 rpm (convert.)
Torque 350 lb-ft @ 3,200 rpm (coupe)
345 lb-ft @ 3,200 rpm (convert.)
Ok 1990 got 5 HP more ....
its because of the added compression ??????
5 HP with flat tops ? its too little
from 9.5 :1 to 10.25:1 its 5 hp ?
Reading is fundamental.
Burning Brakes
Joined: Aug 2000
Posts: 1,146
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From: Albuquerque NM
Let me explain myself better :
1989 :
Compression Ratio 9.5:1
Horsepower 245 hp @ 4,300 rpm (coupe w/ 3.07:1 axle)
240 hp (convert.)
Torque 340 lb-ft @ 3,200 rpm
1990 :
Compression Ratio 10.25:1
Horsepower 250 hp @ 4,400 rpm (coupe)
245 hp @ 4,000 rpm (convert.)
Torque 350 lb-ft @ 3,200 rpm (coupe)
345 lb-ft @ 3,200 rpm (convert.)
Ok 1990 got 5 HP more ....
its because of the added compression ??????
5 HP with flat tops ? its too little
from 9.5 :1 to 10.25:1 its 5 hp ?
1989 :
Compression Ratio 9.5:1
Horsepower 245 hp @ 4,300 rpm (coupe w/ 3.07:1 axle)
240 hp (convert.)
Torque 340 lb-ft @ 3,200 rpm
1990 :
Compression Ratio 10.25:1
Horsepower 250 hp @ 4,400 rpm (coupe)
245 hp @ 4,000 rpm (convert.)
Torque 350 lb-ft @ 3,200 rpm (coupe)
345 lb-ft @ 3,200 rpm (convert.)
Ok 1990 got 5 HP more ....
its because of the added compression ??????
5 HP with flat tops ? its too little
from 9.5 :1 to 10.25:1 its 5 hp ?
Le Mans Master
Joined: May 2007
Posts: 8,448
Likes: 27
From: Valparaiso
nah,this was what i was looking for :
I knew GM has something to do with it
they pussified the 90-91 camshaft specs in order to offset/cut power, as the LT1 was being rolled out and GM could never have claimed a 50chp difference, would have been more like 25-35chp; this doesn't advertise as well and have a nice ring to it that 50hp does.
